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Tuesday, 27 January 2015

Where has that damp smell gone?

No need for these now!
The was always a certain smell when we came back home. That slight dusky smell that reminds you that there was damp in the house. Well, I am glad to say that when we returned from being away at Christmas there was no such gentle reminder.

The mould that has been growing (thanks to the original builders who left the house renderless and with some major defects exposed to some pretty awful weather in the late summer) has been stopped in its tracks. Now, all I need to do is to repaint all the internal areas that have lost their paint / been affected by mould etc.

I am really pleased that our efforts (and that of Welsh Lime Works) have paid off.

In summary we have:

1. Created a drain all around the building so lower the external ground level - this will allow any moisture from the ground to be vented off before reaching internal floor levels

2. Opened up a blocked chimney on the first floor to create a better airflow through the house (the ground floor chimneys house wood burning stoves and so are already open)

3. Removed the cement render from the solid walled and early cavity walled elements of the house and replaced this with a lime putty / limestone dust render. Finished with a white limewash (applied in a hot mix)

4. I have also reset all the guttering to ensure that it is not leaking anywhere

So effectively the house is now functioning as closely to its original design as it is economically viable to do (note that we have not replaced the cement floors with the original suspended floors).

We have experienced some pretty wet weather at times since the work was finished and it should be noted that some areas (concrete block substrate) is still drying out, but the internal walls are now dry and the render is slowly releasing all the trapped water to the outside. 

I had imagined that the drying process would take a lot longer, given that the walls were exposed for so long and that the limewash was only put on late last year, but the project has worked really well and we now have a dry and smell free home. So all bodes well for the future as, apart from routine maintenance on gutters etc, the actual structure of the building is now working in a way that will keep the whole house dry inside for many decades to come. I am expecting that I will need to re-limewash every 6-8 years one the southern and western elevations, but more like every 10-15 years to the north and east (and this is down more to issues of traffic fumes rather than the weather).

Given that I have seen replacement cement render failure in a significant number of solid walled houses within a year of application I think that the added expense of doing it right will soon pay off. It really is a false economy to use cheap materials when all you do is store up more hassle and expense for a future date. So, if you have an old house with a damp problem why not give us a call and we can help you out.

Monday, 26 January 2015

Cavities not immune from damp

Cavity walls were designed to keep damp out of homes
Cavity walls have been the standard way of building for the past century. They are designed to have two walls (bound together by wall ties) with one acting as the external face that can get a little wet and the inner one that is protected by the cavity from this potential moisture ingress.

The cavities were vented to allow air to circulate in them to help dry out any moisture that did make it through to the cavity.

All sounds grand.

However, the system has some issues with it on a number of levels.

1. Initial Build - many cavities were not well formed as cement mortar etc would fall down the cavity during the construction period. This can cause a bridge to be formed across the cavity from the outer wall to the inner.

2. Maintenance - the wall ties that were used to bind the two walls together were mild steel and this rusts. So slowly the failure of the ties can cause cracks to appear in the walls and this requires the home owner to replace the ties when needed. Cracks in render also tend to go un-repaired and re-pointing is not undertaken when needed. These issues mean that water gets trapped in the outer wall, thus making the chances of water ingress across the structure more likely.

3. Improvements - many cavities have been insulated over the past couple of decades. This fills the cavity with material that can cause a bridge to form between the two walls. Some materials that have been used in the past have also failed (mostly foams) and these have slumped to the bottom of the cavity in a bit of a mess. It should also be noted that many houses are not fully filled - companies do not like filling around doors, windows, pipes etc as their products can escape through cracks etc and they don't want the hassle of tidying up, so many cavity walls are not very well insulated.

I have come across a number of houses recently where the wall ties and the use of cement renders has caused damp to find its way into what should be a damp free house. Basically what has happened is that the cracks associated with ties and lack of regular maintenance have let water into the outer wall and trapped it there. On mainly westward facing walls this moisture has then either tracked across ties, through or across the top of the insulation, thus reaching the inner wall. The lack of ventilation in the cavity means that the inner wall then gets wet and stays wet (only drying to the internal space).

So just be aware that cavity walls can be damp and that the fundamental remedies to problem might involve:

Re-rendering or at least repairing the 'blown' render
Re-pointing where required
Removal of old cavity wall insulation and potential insulation replacement once outer wall has been repaired
Replacement wall ties (with new stainless steel ties)

So if you are looking to buy a house make sure that you test all the walls (including upper stories) for damp.

There are of course other issues like insulation at wall plate levels, tying in ceiling and wall insulation etc.

Please remember that we can provide an independent damp report for you that will highlight areas of damp, their root cause and appropriate remedies rather than the standard tick box approach that is taken by the more mainstream industry.

Monday, 12 January 2015

Osmo Sample Sachets

One of the issues with Osmo products up until now has been the issue associated with tester pots.


The brilliant Osmo Polyx Oils, Wood Waxes etc have only been available in the small 125ml tins and these are meant to sell for £9 each. Now this has been a tad steep, especially if you wanted to compare a couple of colours and finishes, however, now there is an answer.

The new 5ml sachet samples. These are ideal for trying Osmo products on a small section of timber. At present they are only available in the internal finish range - Polyx and Wood Wax etc, but soon the exterior range (Wood Oils, Country Colour etc) will be launched.

The new 5ml is a much more realistic £1.20 RRP, but we shall be selling at £1 each.

Polyx Oil range can be found here
Woodwax range can be found here